Only update composited-scrolling state once after layout.

Source/core/rendering/RenderLayerCompositor.cpp

 /*
  * Copyright (C) 2009, 2010 Apple Inc. All rights reserved.
  *
  * Redistribution and use in source and binary forms, with or without
  * modification, are permitted provided that the following conditions
  * are met:
  * 1. Redistributions of source code must retain the above copyright
  *    notice, this list of conditions and the following disclaimer.
  * 2. Redistributions in binary form must reproduce the above copyright
  *    notice, this list of conditions and the following disclaimer in the
@@ skipping 200 matching lines @@
     , m_hasAcceleratedCompositing(true)
     , m_compositingTriggers(static_cast<ChromeClient::CompositingTriggerFlags>(ChromeClient::AllTriggers))
     , m_compositedLayerCount(0)
     , m_showDebugBorders(false)
     , m_showRepaintCounter(false)
     , m_reevaluateCompositingAfterLayout(false)
     , m_compositing(false)
     , m_compositingLayersNeedRebuild(false)
     , m_forceCompositingMode(false)
     , m_inPostLayoutUpdate(false)
+    , m_needsUpdateCompositingRequirementsState(false)
     , m_isTrackingRepaints(false)
     , m_rootLayerAttachment(RootLayerUnattached)
 #if !LOG_DISABLED
     , m_rootLayerUpdateCount(0)
     , m_obligateCompositedLayerCount(0)
     , m_secondaryCompositedLayerCount(0)
     , m_obligatoryBackingStoreBytes(0)
     , m_secondaryBackingStoreBytes(0)
 #endif
 {
@@ skipping 92 matching lines @@
         if (Page* page = this->page())
             page->chrome()->client()->scheduleCompositingLayerFlush();
     }
 }
 
 bool RenderLayerCompositor::hasAnyAdditionalCompositedLayers(const RenderLayer* rootLayer) const
 {
     return m_compositedLayerCount > (rootLayer->isComposited() ? 1 : 0);
 }
 
+void RenderLayerCompositor::updateCompositingRequirementsState()
+{
+    TRACE_EVENT0("blink_rendering", "RenderLayerCompositor::updateCompositingRequirementsState");
+
+    if (!m_needsUpdateCompositingRequirementsState)
+        return;
+
+    m_needsUpdateCompositingRequirementsState = false;
+
+    if (!rootRenderLayer() || !rootRenderLayer()->acceleratedCompositingForOverflowScrollEnabled())
+        return;
+
+    const FrameView::ScrollableAreaSet* scrollableAreas = m_renderView->frameView()->scrollableAreas();
+    if (!scrollableAreas)
+        return;
+
+    RenderLayer::AncestorContainingBlockMap map;
+    for (HashSet<RenderLayer*>::iterator it = m_outOfFlowPositionedLayers.begin(); it != m_outOfFlowPositionedLayers.end(); ++it)
+        (*it)->updateHasUnclippedDescendant(map);
+
+    for (FrameView::ScrollableAreaSet::iterator it = scrollableAreas->begin(); it != scrollableAreas->end(); ++it)
+        (*it)->updateNeedsCompositedScrolling();
+}
+
 void RenderLayerCompositor::updateCompositingLayers(CompositingUpdateType updateType, RenderLayer* updateRoot)
 {
     // Avoid updating the layers with old values. Compositing layers will be updated after the layout is finished.
     if (m_renderView->needsLayout())
         return;
 
     if (m_forceCompositingMode && !m_compositing)
         enableCompositingMode(true);
 
     if (!m_reevaluateCompositingAfterLayout && !m_compositing)
@@ skipping 137 matching lines @@
 #ifndef NDEBUG
     layerName = layer->debugName();
 #endif
 
     LOG(Compositing, "%*p %dx%d %.2fKB (%s) %s\n", 12 + depth * 2, layer, backing->compositedBounds().width(), backing->compositedBounds().height(),
         backing->backingStoreMemoryEstimate() / 1024,
         logReasonsForCompositing(layer), layerName.utf8().data());
 }
 #endif
 
+void RenderLayerCompositor::addOutOfFlowPositionedLayer(RenderLayer* layer)
+{
+    m_outOfFlowPositionedLayers.add(layer);
+}
+
+void RenderLayerCompositor::removeOutOfFlowPositionedLayer(RenderLayer* layer)
+{
+    m_outOfFlowPositionedLayers.remove(layer);
+}
+
 bool RenderLayerCompositor::updateBacking(RenderLayer* layer, CompositingChangeRepaint shouldRepaint)
 {
     bool layerChanged = false;
     RenderLayer::ViewportConstrainedNotCompositedReason viewportConstrainedNotCompositedReason = RenderLayer::NoNotCompositedReason;
 
     if (needsToBeComposited(layer, &viewportConstrainedNotCompositedReason)) {
         enableCompositingMode();
         
         if (!layer->backing()) {
             // If we need to repaint, do so before making backing
@@ skipping 2259 matching lines @@
     info.addMember(m_layerForScrollCorner, "layerForScrollCorner");
 #if ENABLE(RUBBER_BANDING)
     info.addMember(m_layerForOverhangAreas, "layerForOverhangAreas");
     info.addMember(m_contentShadowLayer, "contentShadowLayer");
     info.addMember(m_layerForTopOverhangArea, "layerForTopOverhangArea");
     info.addMember(m_layerForBottomOverhangArea, "layerForBottomOverhangArea");
 #endif
 }
 
 } // namespace WebCore